The use of transmit-receive modules (TRMS) has become a popular method of exciting the antennas associated with phased array radar instruments. The use of such modules enables RF power to be developed at a number of sites across the antenna. Typically this is a large number. The peak RF power required to provide the required level of radar instrument functionality can then be generated in small portions in each of the TRMs and united into a single pulse of RF power in the region of air/space in front of the antenna.
The provision of such RF power creates demands for energy within the TRM. This energy is conventionally acquired from short-term energy stores, typically from a bank of capacitors. However, the finite amount of energy that can be stored in such capacitors coupled with the rapid rate at which such energy is discharged of energy from them during the period when the TRM is required to produce a pulse of RF energy, imposes a significant constraint on the duration of pulse that can be generated by the TRM. The typical duration of such pulses is between microseconds and hundreds of microseconds.
The need for such capacitors introduces considerable complexity into TRM design for radars in which the transmitter is required to transmit continuously for periods longer than hundreds of microseconds. In particular, in cases where the radar is required to provide continuous rather than pulsed illumination of a region of interest, a different means of operating TRMs has to be used.
During pulsed operation, the mean current needed to replenish such capacitors after each pulse of RF power generation, leads to a need for significant DC power conditioning circuits within each TRM, and the need for wire conductors of appreciable cross-sectional area to convey electrical power to the power conditioning elements in each TRM. The power conditioning circuits in each TRM take electrical power from the external source, for instance—from the main electrical power bus that is made available to electrical equipments in most spacecraft/satellites, and converts that available power into the specific supply voltages that may be needed by individual electrical circuits within the TRM.